Unhairing bath and process for treating hides



Patented Got. 16, 1934 lJNlTED GFFICE UNHAIRING BATH AND PROCESS FOR TREATING HIDES No Drawing. Application March 15, 1932,

Serial No. 599,059

20 Claims. (01. 149-2) The invention relatesto baths for unhairing hides, and includes a process for treating hides to efiect the removal of hair therefrom. Unhairing baths are useful in recovering wool or other hair for textile purposes, but their principal application is in the preparation of hides for tanmng.

Hides are normally received at the tannery after curing by sun-drying or salting. At the tannery the hides are soaked to cleanse and rehydrate them. Soaking is usually done in plain water and is'continued until all the salt, in the case of salt cured hides, is eliminated from the hide. plumped, and finally tanned.

In general practice the unhairing and plumping operations are carried out together, as by treating the hides for two or three days in a bath prepared by suspending lime in water, and then adding sodium sulfide. Such a bath decomposes the epidermis, or outer layer of the hide; and since the epidermis lines the hair follicles and grips the hairs the latter are loosened so that they can be removed mechanically. At the same time the corium (which underlies the epidermis and forms the substance of the finished leather) swells, takes on a firmer texture, and is otherwise modified so that it becomes amenable to tanning. This effect is called plumping, and additional agents may or may not be added to the bath to produce the desired degree of plumping.

In accordance with the invention, aliphatic primary, secondary, or tertiary amines in physical or chemical combination with sulfur are'used as dehairing agents. Thus, amine sulfides or sulfites, sulfur dissolved in amine solutions, and finely dispersed or colloidal sulfur in conjunction with known depilatory agents, alone or in conjunction with lime are examplesof my improved dehairing agents.

The invention is illustrated by the following examples, but is not to be considered as limited thereby:

I. Hydrogen sulfide gas was bubbled through a 50% solution of ethylene diamine in water. Heat was evolved and a yellow solution was obtained. This product will be designated as ethylene diamine sulfide.

An unhairing bath was prepared equal to four times the weight of soaked calfskin to be unhaired. This bath contained 1% of the weight of soaked hides of ethylene diamine sulfide, and 10% of the weight of soaked hides of a 20% suspension of freshly slaked lime. After 24 hours of treatment in this solution the calfskins were The hides are thereafter unhaired,

readily unhaired. The same amount of lime alone did not unhair in several days time.

Ethylene diamine sulfide was as effective as the same quantity of sodium sulfide (a common depilatory agent). In each case the hair was destroyed, but the hides after the ethylene diamine sulfide treatment were softer and lighter in color than those unhaired with sodium sulfide. Ethylene diamine also is advantageous in that it serves as a carrier for sulfides, and retains as a suspension in the solution any calcium sulfide which may be formed. Calcium sulfide as such is insoluble and is valueless in unhairing.

Other amines, including methylamine and mono, di, and triethanolamines may be used in :0 the same manner as ethylene diamine, and their sulfides are satisfactory unhairing agents.

II. Flowers of sulfur were dissolved in 50% solutions of triethanolamine, monoethanolamine, and ethylene diamine; in a 34% solution of methylamine; and in a 95% solution of diethanolamine. Ethylene diamine dissolved the most sulfur, methylamine about the same amount, mono and diethanolamine a lesser amount, and triethanolamine the least.

A crystalline flaky precipitate which was quite stable was obtained from the ethylene diamine solution. Calfskins were satisfactorily unhaired after 70 hours treatment in a solution containing 5% of this precipitate and 5% of lime based on the weight of soaked skins. All of the amine solutions containing dissolved sulfur exhibited increased unhairing power over ordinary depilatory or plain amine solutions. In each case the time required for satisfactory unhairing was decreased by increasing the amount of amine-sulfur solution in the unhairing bath. It was also discovered that a mixture of equal parts of the ethylene diamine and methylamine sulfur solutions in conjunction with lime was better than either solution alone.

The solutions described in this example are true solutions rather than chemical combinations, since an excess of water will precipitate the sulfur. The amine-sulfur solutions possess the advantage of producing lighter colored and softer hides than known depilatories, and unlike strongly alkaline depilatories, such as sodium sulfide, they do not destroy the hair.

III. Solutions of amine sulfites were prepared by bubbling sulfur dioxide into the amine solutions. These solutions were then used as in Example I, and the following amine sulfites were found to be satisfactory depilatories: ethylene di- 110 amine, methylamine, monoethanolamine, and diethanolamine.

IV. The. amine sulfides described in Example I may be made into pastes for unhairing sheepskins. Of these, ethylene diamine, methylamine, and monoethanolamine sulfides produced the best results. For example, a paste consisting of 5% ethylene diamine sulfide, 15% lime and 80% water unhaired satisfactorily in 20 to 24 hours. The paste is applied to the flesh side of the skin in order to avoid destroying the wool.

The advantages of amine sulfides in depilatory pastes for sheepskins may be listed as follows. in which the new unhairing a ents are compared to sodium sulfide, the usual depilatory:

Sodium sulfide is a solid, diificult to dissolve, and its solutions and pastes must be kept hot to prevent crystallization of the sodium sulfide. The sodium sulfide crystallizes in the brushes by which the paste is applied and quickly destroys them.

Amine sulfides may be handled in concentrated solutions, and when solid are readily dissolved. The amine sulfides are soluble in cold water, and the pastes may be used cold. The amine sulfide does not crystallize out of the paste easily. Amine sulfide pastes are thicker in consistency than those made from sodium sulfide. Thin pastes tend to flow over the edges of sheep skins, and destroy the wool. T

In all cases, hides unhaired with amine-sulfur chemical or physical combinations are in better condition than those unhaired with previously known agents. The hair is completely removed without leaving the roots in the skin. The amine unhairing baths exert a distinct cleansing effect on the hides producing a cleaner, lighter colored hide. The hide also has a softer, finer texture when treated in accordance with the invention. In those cases in which the hair is not destroyed the hair removed is in better condition since all of the fiber length, including the roots of the hairs is recovered. g

In addition to the unhairing baths disclosed, modified embodiments of the invention are possible. For example, alkali hydroxides, such as sodium or potassium hydroxide, or other strong alkalies in small amounts may be added to the unhairing baths of my invention. Also, I have found that finely dispersed or colloidal sulfur alone in conjdnction with lime in unhairing baths increases the efficaciousness of such baths.

agents of the group consisting of chemical and physical combinations of sulfur with aliphatic amines.

5. An unhairing bath containing depilatory agents of the group consisting of chemical and physical combinations of sulfur with aliphatic, amines in conjunction with inorganic compounds having an alkaline reaction.

6. An unhairing bath containing depilatory agents of the group consisting of chemical and physical combinations of sulfur with aliphatic amines in conjunction with lime.

7. An unhairing bath containing depilatory agents of the group comprising the sulfites of aliphatic amines.

8. An unhairing bath containing depilatory agents of the group comprising the sulfites of ethylene diamines, methylamine, monoethanolamine, diethanolamine, and triethanolamine.

9. An unhairing bath containing depilatory agents of the group comprising the sulfites of aliphatic amines in conjunciton with lime.

10. An unhairing bath containing depilatory agents of the group comprising the sulfites of ine, and triethanolamine in conjunction with lime.

. 14. Process of unhairing hides which comprises subjecting the hides to the action of an unhairing bath containing sulfur in physical combination with a depilatory agent comprising an aliphatic amine until the hair is loosened.

15. Process of unhairing hides which comprises subjecting the hides to the action of an unhairing bath containing sulfur in physical combination with depilatory agents comprising aliphatic amines and lime until the hair is loosened.

16. Process of unhairing hides which comprises subjecting the hides to the action of an unhairing bath containing depilatory agents of the group consisting of chemical and physical combinations of sulfur with aliphatic amines until the hair is loosened.

17. Process of unhairing hides which comprises subjecting the hides to the action of an unhairing bath containing depilatory agents of the group consisting of chemical and physical combinations of sulfur with aliphatic amines in conjunction withlime until the hair is loosened.

,18. Process of-unhairing hides which comprises consisting of physical solutions of sulfur in solutions of aliphatic amines.

20. Process of unhairing sheepskins which com- 3 prises applying to the flesh side of the sheepskins a paste containing a sulfide of an aliphatic amine of the group comprising ethylene diamine, methyl amine, and monoethanolamine and lime, and allowing said paste to remain on said skin until the wool is loosened.

NORMAN D. HARVEY, Ja. 

